How to Test an ABS Wheel Speed Sensor with a Multimeter

An ABS warning light often means a wheel speed sensor has failed. Before buying a replacement, you can test the old one with a simple multimeter to confirm the diagnosis.

Identifying the Sensor Type

There are two main types: passive (magnetic coil) and active (Hall effect). Passive sensors have two wires and generate their own AC voltage. Active sensors have three wires and need power to operate.

Testing a Passive Sensor

Set your multimeter to AC Volts. Spin the wheel by hand while probing the sensor connector. You should see a small voltage fluctuation (usually increasing with speed). If there is no voltage, check the resistance (Ohms). An open circuit (infinite resistance) means the internal coil is broken. Replacing a bad sensor is usually a quick bolt-on job that clears your dashboard lights instantly.